Effects of short-term norepinephrine infusion on plasma catecholamines, renin, and aldosterone in normal and hypertensive man.

The acute responsiveness of plasma catecholamine, renin (PRA), and aldosterone levels to exogenous norepinephrine was studied under placebo conditions and following renin (PRA), and aldosterone levels to exogenous norepinephrine was studied under placebo conditions and following renin-angiotensin activation by diuretic pretreatment in 25 normal subjects and 34 patients with borderline-to-moderate essential hypertension. Norepinephrine infusion caused increases in plasma norepinephrine (PNE) that correlated with the infused norepinephrine dose (p < 0.001); this relationship was similar in normal and hypertensive subjects and unaltered by diuretic therapy. Plasma epinephrine and dopamine levels were unchanged during norepinephrine infusion. Norepinephrine infusion at pressor doses stimulated PRA (p < 0.01). The PRA responses correlated with the dose of infused norepinephrine (p < 0.0025), and norepinephrine-stimulated PRA correlated with basal PRA (p < 0.001). These norepinephrine-PRA relationships were unaltered by diuretic treatment and similar in normal and hypertensive subjects. In both groups, norepinephrine also caused a similar increase in plasma aldosterone (p < 0.05) under placebo conditions, but not following diuretic therapy. These findings demonstrate that an acute increase in the blood levels of the adrenergic neurotransmittor, norepinephrine, causes mild but distinct stimulation of plasma renin and aldosterone levels. Renin release in response to exogenous norepinephrine is not enhanced following renin-angiotensin activation by diuretic pretreatment. The responsiveness of the renin-angiotensin-aldosterone system to an acute norepinephrine input seems to be intact in essential hypertension.